Interest rates are compensation for the time-value of money, and are calculated on judgments (the amount of money one party to a lawsuit is ordered to pay another party) based on the applicable state or federal statutes. There are often different interest rates set by law for prejudgment interest (the interest on the amount owed before the judgment) and post-judgment interest (the interest on the amount owed after the judgment). The calculation of prejudgment and post-judgment interest rates vary from state to state (and in federal court), and require a careful analysis of the statutes.

In Missouri, interest rates on judgments are governed by state statutes, which set forth the rates for both prejudgment and post-judgment interest. Prejudgment interest is designed to compensate a plaintiff for the loss of use of money due to the defendant's wrongful conduct from the time of loss to the time of judgment. Missouri law allows for prejudgment interest in certain circumstances, and the rate is often specified in the contract or determined by the court if not specified. Post-judgment interest, on the other hand, is interest that accrues on the amount of the judgment from the date the judgment is entered until the judgment is paid. In Missouri, the post-judgment interest rate is set by statute and can vary, but it is typically calculated at an annual rate that is adjusted according to the market rates, with a minimum and maximum possible rate. It is important to consult the current Missouri statutes or an attorney to determine the exact interest rates applicable to a specific judgment, as these rates can change over time.